The syntheses of 4b,5a-dihydro-5H-benzo[3,4]-phenanthro[1,2-b]azirine and 1a,11b-dihydro-6,11-dimethyl-1H-benz[3,4]anthra[1,2-b]azirine

The syntheses of the K-imine derivatives of carcinogenic benzo[c]phenanthrene and 7,12-dimethylbenz-[a]anthracene are described. Treatment of trans-5-azido-5,6-dihydrobenzo[c]phenanthren-6-ol ( 3 ) and trans-6-azido-5,6-dihydrobenzo[c]phenanthren-5-ol ( 5 ) with thionyl chloride yielded the corresponding β-chloro azides, which in turn, were reacted with lithium aluminium hydride to give 4b,5a-dihydro-5H-benzo[3,4]-phenanthro[1,2-b]azirine ( 2 ). In a similar manner trans-5-azido-5,6-dihydro-7,12-dimethylbenz[a]anthracen-6-ol ( 11 ) and trans-6-azido-5,6-dihydro-7,12-dimethylbenz[a]anthracen-5-ol ( 13 ) were transformed to the respective chloro azides and, converted into 1a,11b-dihydro-6,11-dimethyl-1H-benz[3,4]anthra[1,2-b]azirine ( 10 ).     

Spatial Configuration of Derivatives of 5,5a,6,7-Tetrahydropyrido[1,2-a]benzimidazole and 6,7-Dihydro-5aH-pyrido[1,2-b]benzoxazole

The spatial configurations of 7,9-diphenyl-5a,6-tetramethylene-5,5a,6,7-tetrahydropyrido[1,2-a]benzimidazole and 7,9-diphenyl-5a,6-tetramethylene-2,5a,6,7-tetrahydropyrido[1,2-a]benzimidazol-2-one have been established by X-ray crystallography. Analogous configurations are proposed for a series of other derivatives of 5,5a,6,7-tetrahydropyrido[1,2-a]benzimidazoles and some derivatives of 6,7-dihydro-5aH-pyrido[1,2-b]benzoxazoles on the basis of ¹H NMR spectroscopic data and the results of quantum chemical calculations using the MNDO, AM1, and PM3 methods.     

Formylation of Furyl-substituted Imidazo[1,2-a]pyridine, Imidazo[1,2-a]pyrimidine and Imidazo[2,1-b]thiazole

Vilsmeier formylation of 2-(2-furyl)-substituted imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, and also 6-(2-furyl)imidazo[2,1-b]thiazole with 1 mole of reagent occurs at the free position of the imidazole ring, while with an excess of the reagent it also occurs at the position 5 of the furyl group.     

Synthesis of fluorantheno[1,2-b]thiophene and fluorantheno[3,2-b]thiophene,isosteres of benzofluoranthenes

The total syntheses of fluorantheno[1,2-b]thiophene and fluorantheno[3,2-b]thiophene are reported. The common cyclobutanone intermediate which was obtained by [2 + 2] addition of fluorenylidene ketene with 2,3-dihydrothiophene underwent regioselectively α or β ring opening to lead to linear or angular PAC skeleton molecules under desired conditions. 2,3-Dichloro-5,6-dicyanobenzoquinone was applied for aromatization to achieve the formation of PAC's. These two isosteres exhibit very similar uv/visible spectra to benzo[a] and [b]fluoranthenes respectively. Spectroscopic data used for their structural assignments is also discussed.     

The synthesis of 11H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]indoles,11H-tetrazolo[4,5-b]pyridazino[4,5-b]indoles and 1,2,4-triazolo[3,4-f]-1,2,4-triazino[4,5-a]indoles

This paper describes the synthesis of the previously unknown 11H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]indoles (2) and 11H-tetrazolo[4,5-b]pyridazino[4,5-b]indoles (3) from 4-hydrazino-5H-pyridazino[4,5-b]indoles (1) , as well as the synthesis of 1,2,4-triazolo[3,4-f]-1,2,4-triazino-[4,5-a]indoles (10) from 2-indolecarbohydrazide (4) . Compounds 2 were obtained by acylation of compounds 1 , followed of thermal cyclization and compounds 3 by treating compounds 1 with nitrous acid. The reactions of compound 4 with formic acid or ethyl orthoformiate gave 1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indole (6) . Treating this last compound with phosphorus oxychloride or phosphorus pentasulfide, followed by hydrazine, gave 1-hydrazino-1,2,4-triazino-[4,5-a]indole (9) . Acylation of this last compound, followed of cyclization gave compounds 10 . All the compounds were characterized by elemental analysis and ir and ¹H-nmr spectra.     

Transformations of the pyrido[1,2-a]pyrazine ring system into imidazo[1,2-a]pyridines,imidazo[1,2-a]pyrimidines and 2-oxa-6a, 10c-diazaaceanthrylenes

Transformations of methyl 3-dimethylamino-2-(1-methoxycarbonyl-4-oxo-4H-pyrido[1,2-a]pyrazin-3-yl)acrylate with some cyanomethylenecarbonyl group containing compounds or cyanamide into imidazo-[1,2-a]pyridines, irmdazo[1,2-a]pyrimidines and 2-oxa-6a, 10c-diazaaceanthrylenes are described.     

Polycyclic systems: Synthesis of isoindolo[2,1-b]-pyrrolo[1,2-d][2,4]benzodiazocine and isoindolo-[1,2-d]pyrrolo[1,2-a] [1,5]benzodiazocine

The synthesis of isoindolo[2,1-b]pyrrolo[1,2-d][2,4]benzodiazocine 7 and isoindolo[1,2-d]pyrrolo[1,2-a]-[1,5]benzodiazocine 13 are described starting from 2-(2-methoxycarbonyl)benzylphthalimide 1a and ethyl α-bromohomophthalate 9 respectively.     

Thermolyzed products of naphth[1,2-d]imidazo[2,1-b]-thiazole-2,3-dione

Themolysis of naphth[1,2-d]imidazo[2,1-b]thiazole-2,3-dione ( 1 ) in dimethylformamide gave an intermediate 2-isocyanatonaphtho[1,2-d]thiazole ( 2 ), which underwent [4 + 4] cyclodimerization to yield dinaphtho-[1″,2″:4,5;1′″,2′″:4′,5′]dithiazolo[3,2-a:3′,2′-e]-1,3,5,7-tetrazocine-9,19-dione ( 3 ). The possible [4 + 2] cycloadduct, 3-(2-naphtho-[1,2-d]-thiazolyl)naphtho[1′,2′:4,5]thiazolo[3,2-a]-1,3,5-triazine-2,4-dione ( 4 ), an usual dimer type of heterocyclic isocyanates was not produced. Discrimination between the two isomers was established on the basis of spectral analyses.     

The synthesis of 7,8-dihydroimidazo[1,2-e]pyrazolo[1,5-a]-1,3,5-triazines, 8,9-dihydro-7H-pyrimido[1,2-e]pyrazolo[1,5-a]-1,3,5-triazines and 7,8,9,10-tetrahydro[1,3]diazepino[1,2-e]pyrazolo[1,5-a]triazines

Cyclic hydrazino amidines were converted to the corresponding aminopyrazolyl derivatives. Ring closure between the amino groups of pyrazoline moieties and NH groups of cyclic amidines afforded the following ring systems: 7,8-Dihydroimidazo[1,2-e]pyrazolo[1,5-a]-1,3,5-triazines, 8,9-dihydro-7H-pyrimido[1,2-e]pyrazolo[1,5-a]-1,3,5-triazines and 7,8,9,10-tetrahydro[1,3]diazepino[1,2-e]pyrazolo[1,5-a]-1,3,5-triazines.     

1,2-Fused pyrimidines. III. Derivatives of 12H-pyrido[1′,2′:1,2]pyrimido[4,5-b]quinoline,a novel heterocyclic system

Reactivities of 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones and 4-amino-2H-pyrido[1,2-a]pyrimidin-2-ones, both N,N-dialkyl and (N-alkyl, N-phenyl)substituted, when treated with the N,N-dimethylformamide/phosphorus oxychloride Vilsmeier-Haack reagent XII were compared. Starting from 2-[(N-alkyl, N-phenyl)amino] compounds IXa,b , the expected XVIa,b and XVIIa,b were obtained, which are derivatives of 12H-pyrido[1′,2′:1,2]pyrimido[4,5-b]quinoline, a novel heterocyclic system. When 2-(phenylamino) compound IXc was used a mixture of 3-formylderivative XVIII and 12H-pyrido-[1′,2′:1,2]pyrimido[4,5-b]quinolin-12-one ( XIX ) resulted from the reaction. On the other hand, 2-(dialkylamino)-4H-pyrido[1,2-a]pyrimidin-4-ones IIIa-c plainly afforded high yields of 3-formylderivatives XIVa-c. In contrast, no significant reaction occurred when 4-(dialkylamino) and 4-[(N-alkyl,N-phenyl)amino] compounds IIa-c and VIIIa,b were treated with the reagent XII , under the same as well as more severe conditions. A clear difference in the nucleophilic reactivity of C-3 position between these two classes of isomers is pointed out by the above summarized results.     

The photo cycloaddition of alkenes to s-triazolo[4,3-b] and [2,3-b]pyridazines

s-Triazolo[4,3-b]pyridazine (I) reacted with cyclohexene under the influence of ultraviolet light to yield 4a,5,7,8,8a,9-hexahydro-9-methylene-6H-s-triazolo[1,5-a]indole (IV) and 9-cyanomethyl-4a,5,7,8,8a,9-hexahydro-6H-s-triazolo[1,5-a]indole (V). These products were formed by the addition of the alkene to the 1,8 positions of I with a concurrent cleavage of the N₄? N₅ bond. Similar additions were observed with cyclopentene and 2,3-dimethyl-1,3-butadiene. The isomeric s-triazolo[2,3-b]pyridazine (III) reacted with cyclohexene to form an isomer of IV, 4a,5,7,8,8a,9-hexahydro-9-methylene-6H-s-triazolo[4,3-a]indole (XV) and two [2 + 2] cycloadducts (XVI and XVII).     

Derivatives of benzo[5,6]cyclohepta[1,2-b]thiophene. Synthesis of 2,3,7,8-tetrahydro-3-oxothieno[1,2-b]cyclohepta[5,6,7-de]isoquinoline and 1,2,3,7,8,11b-hexahydro-3-oxothieno[1,2-b]cyclohepta[5,6,7-de]isoquinoline

The synthesis of the title compounds was carried out by cyclization via isocyanate of (E)-4,5-dihydro-10H-benzo[5,6]cyclohepta[1,2-b]-thiophene-10-ylideneacetic acid and 4,5-dihydro-10H-benzo[5,6]cyclohepta[1,2-b]-thiophene-10-ylacetic acid respectively, which were obtained by the Wadsworth-Emmons modification of the Wittig reaction of 4,5-dihydro-10H-10-oxobenzo[5,6]cyclohepta[1,2-b]thiophene and triethyl phosphonacetate. The structures of these new compounds are described.     

One-pot synthesis of chromeno[2,3-b]isoindolo[1,2-e]pyrrole-12,13-dione derivatives by sequential reaction of ninhydrin, 2-aminochromen-4-ones and arylamines

Stirring an equimolar mixture of ninhydrin 1 and 2-aminochromen-4-ones 2 in CH₃COOH at room temperature produced 6a,11a-dihydroxy-6H-chromeno[2,3-b]indeno[2,1-d]pyrrole-11,12(6aH,11aH)-diones 3, which on heating with aromatic amines 6 in acetic acid produced 11b-hydroxy-7-N-arylimino-6H-chromeno[2,3-b]isoindolo[1,2-e]pyrrole-12,13(11bH)-diones 7.     

Synthesis of novel imidazo[1,2-a]pyrrolo[2,1-c][1,4]benzodiazepines and pyrimido[1,2-a]pyrrolo[2,1-c][1,4]benzodiazepines

Several 1 1-amino-5H-pyrrolo[2,1-c][1,4]benzodiazepines have been used as starting material to prepare a number of derivatives of 9H-imidazo[1,2-a]pyrrolo[2,1-c][1,4]benzodiazepines and 10H-pyrimido[1,2-a]pyrrolo[2,1-c][1,4]benzodiazepines. The imidazole nucleus was built by reaction of amidines with ethyl bromopyruvate or aminoacetaldehyde dimethylacetal. Several derivatives of imidazo[1,2-a]pyrrolo[2,1-c][1,4]benzodiazepine have been prepared by formylation of the pyrrole ring followed by formation of thioamides. Condensation of 11-amino-5H-pyrrolo[2,1-c][1,4]benzodiazepines with diethyl ethoxymethylenemalonate afforded intermediate diesters which were transformed into the corresponding 10H-pyrimido[1,2-a]pyrrolo[2,1-c]-benzodiazepines.     

Syntheses of 10-Oxo-10H-pyrido[1,2-a]thieno[3,4-d]pyrimidines and 10-Oxo-10H-pyrido[1,2-a]thieno[3,2-d]pyrimidines from methyl tetrahydro-4-oxo-3-thiophenecarboxylate and methyl tetrahydro-3-oxo-2-thiophenecarboxylate,respectively

A general synthesis of 10-Oxo-10H-pyrido[1,2-a]thieno[3,4-d]pyrimidines and 10-Oxo-10H-pyrido[1,2-a]-thieno[3,2-d]pyrimidines is described. Methyl tetrahydro-4-oxo-3-thiophenecarboxylate ( 13 ) was condensed with 6-aminonicotinic acid ( 18 ) to give 3,10-dihydro-10-oxo-1H-pyrido[1,2-a]thieno[3,4-d]pyrimidine-7-carboxylic acid ( 19 ). Treatment of 19 successively with chlorotrimethylsilane, N-chlorosuccinimide and water gave 10-oxo-10H-pyrido[1,2-a]thieno[3,4-d]pyrimidine-7-carboxylic acid ( 17 ). Methyl tetrahydro-3-oxo-2-thiophenecarboxylate ( 21 ) was converted to 10-oxo-10H-pyrido[1,2-a]thieno[3,2-d]pyrimidine-7-carboxylic acid ( 25 ) by an analogous route.     

Dipyrrolo[1,2-a:2',1'-c]pyrazines. 8. Electrophilic Substitution in Dipyrrolo[1,2-a:2',1'-c]pyrazines and 5,6-Dihydrodipyrrolo[1,2-a:2',1'-c]pyrazines. Acylation of Dipyrrolo[1,2-a:2',1'-c]pyrazines

Esters, nitriles, and amides of dipyrrolo[1,2-a:2',1'-c]pyrazines have been synthesized by the acylation of dipyrrolo[1,2-a:2',1'-c]pyrazines and 5,6-dihydrodipyrrolo[1,2-a:2',1'-c]pyrazines with trichloroacetic acid chloride, p-tosyl isocyanate, and isocyanatophosphoric acid dichloride (Kirsanov isocyanate).     

Pd-catalyzed oxidative cross-coupling of imidazo[1,2-a]pyridine with arenes

A facile method for direct Pd(OAc)₂-catalyzed oxidative cross-coupling of unactivated imidazo[1,2-a]pyridine with simple arenes has been developed. The reaction shows good reaction efficiency, high regioselectivity, and good functional-group compatibility. This approach provides a useful protocol for the preparation of imidazo[1,2-a]pyridine–arene structure of interest in biological and pharmaceutical materials.     

Synthesis of Structurally Related Purines: Benzimidazo[1,2-a]pyridines, Benzimidazo-[1,2-c]pyrimidines, and Pyrazolo-[1,5-a]pyrimidines

Summary.  Reactions of sodium salts of 3-hydroxymethylene-2-alkanones with 2-cyanomethylbenzimidazole afforded benzimidazo[1,2-a]pyridines. Analogues reactions with 2-aminobenzimidazole and 5-aminopyrazoles afforded benzimidazo[1,2-c]pyrimidines and pyrazolo[1,5-a]pyrimidines. Received December 12, 1999. Accepted (revised) February 12, 2000     

Anomalous fluorescence spectrum of azuleno[1,2-b]pyrrole

Electronic and fluorescence spectra of azuleno[1,2-b]pyrrole, which is an iso-π-electron system of benz[a]azulene, have been measured. The an     

The preparation of the benzo[4,5]cyclohepta[1,2-b]pyrazine and benzo[4,5]cyclohepta[1,2-b]quinoxaline systems

Benzo[4,5]cyclohepta[1,2-b]quinoxaIine 2 , benzo[4,5]cyclohepta[1,2-b]pyrazine 3a and benzo[4,5]cyclohepta[1,2-b]quinoxaline 4 were prepared from 4,5-benzotropolone and 1,2-phenylenediamine, ethylenediamine and 1,2-diaminocyclohexane, respectively. Compound 3a was methylated to 3b .